Connecting strip



E May 12, l959 P. VAN LEEUWEN 2,886,745

coNNEcTlNG STRIP Filed Dec. 5, 1955 INVENTOR PIETER VAN LEEUWEN illCONNECTING STRIP pany, Inc., New York, N.Y., a corporation of DelawareApplication December 3, 1953, Serial No. 396,018

Claims priority, application Netherlands December 5, 1952 6 Claims. (Cl.317-112) The invention relates to a connecting strip comprising a numberof connecting or Contact members which are insulated from one another,more particularly a struc tural element of a bank of contacts for use inautomatic telephone systems and the like.

It is known to construct banks of contacts by piling upon one another anumber of connecting strips each comprising a row of contact memberswhich generally project beyond the edge of the strip on both sides.Usually the ends at one side of the strip are intended for theattachment of the multiple cables, the ends at the other side forco-operation with a moving contact member, The known connecting stripsfor this purpose are usually formed by gripping a row of contact membersbetween insulating strips or, as is more usual, by casting or pressingan insulating plastic mass in a mould so as to surround the row ofcontact members, whereupon the insulating mass is hardened. Theconnecting strips manufactured in this manner have a limitation in thatthe limited accuracy of finishing and the distortion of the insulatingmaterial, such as shrinkage in cooling, necessitate the acceptance ofcomparatively large tolerances. Not only comparatively large dimensionaldepartures must be permitted in the relative spacing of the Contactmembers but also departures in the relative position of the rows ofcontacts of a number of connecting strips composing a bank of contactsare inevitable. The aforesaid results in that a bank of contacts for aselector switch for use in automatic telephone systems comprising adetermined number of contacts per layer must have a definite minimumsize for it is necessary that in every rest position of the brushcarriage of the selector the brushes co-operate correctly with the bankcontacts. Thus, the relative spacings of the contact members due to thetolerances mentioned cannot be as small as would otherwise be possible.

As a rule the rst stage in the manufacture of the known connectingstrips comprising liat contact members is to punch a metal plate so asto produce a row of contact members which are mutually correctlypositioned and the ends of which are connected to a remaining part ofthe plate. After this interconnected row of contact members has beenaccommodated in the connecting strip the plate parts connecting the endsof the contact members are cut away. This method has a limitation inthat it results in a large loss of material.

The primary object of the invention is to provide a connecting stripcomprising a number of contact members which are insulated from oneanother, which strip can be manufactured with small tolerances, the lossof material in forming the contact members being very small. Due tothese small tolerances which also permit the accurate piling of a numberof connecting strips according to the invention so as to obtain a bankof contacts it is possible either while retaining definite dimensions toallow for more contact members in each row, or while retaining adefinite number of contact members in each row to reduce the dimensionsof the strip. This hired States Patent l ice 2 has the advantage that ina bank of contacts for a se-Y lector built up from such strips morecontacts can be covered per unit of time without the mass forcesproduced by accelerating and arresting the brush carriage beingincreased. This is of particular importance in direct telephone systems,that is, systems without registers.

According to the invention the connecting strip consiste of a metalsupporting strip comprising transverse bores in which lengths of metalwires projecting on both sides of the strip are centered by means of aninsulating mass, for example polystyrene or some other synthetic resin.

Since the supporting strip is made of metal, in view of a light 'weightpreferably of aluminum which may be anodized, it can be manufacturedwith very small tolerance. In addition, the connecting or contactmembers formed by the lengths of wire are all screened from one anotherelectrically.

Preferably the insulating mass at the end of a bore is provided with aconical surrounding the length of wire centered in this bore to ensure asuicient creeping path.

To obtain firm anchoring of the lengths of wire in the insulating massthe parts imbedded in the insulating mass preferably comprise atiattening or some other deformation.

The connecting strip according to the invention may be designed so thatthe parts of the contact members extending beyond the edge of thesupporting strip are shaped in the usual hat form. This only requiresthe lengths of Wire to be flattened at one or both ends. As a rule thisflattening can only be carried out after the attachment of the length ofwire in the bores since othen wise the flattened parts prevent thelengths of wire from being introduced into the bores. If the dimensionsof the flattened parts are such that the latter condition does not applyor if only one end of the length of wire is flattened, the attening mayalso be carried out before the lengths of wire are secured in thesupporting strip, To ensure a great accuracy in the relative spacings ofthe fiat ends of the contact members preferably the fiattened ends ofall the contact members arranged in the supporting strip aresimultaneously punched to the desired size by means of a cutting tool.Locating holes or alternative means of alignment provided in or at themetal supporting strip allow this supporting strip and the cutting toolto be arranged in an accurately determined relative position Which maybe reproduced for each supporting strip with the result that not onlythe Contact members of one connecting strip are at a correct relativeposition but also that the connecting strips ex hibit a high degree ofsimilarity. The means of alignment may also be used to ensure a correctrelative position of the strips when a number thereof are piled upon oneanother.

The invention will now be described with reference to one embodimentthereof given by way of example and shown in the accompanyingdiagrammatic drawing, in which Fig. 1 is a plan view of a firstembodiment of a connecting strip according to the invention of whichFigs. 2 and 3 show cross-sections taken along the lines II-II andIII-III.

Fig. 4 is a cross-sectional View corresponding with that shown in Fig. 2of a second embodiment of the connecting strip according to theinvention.

Referring now to the figures, the connecting strip shown in Figs. l, 2and 3 consists of a flat strip-shaped support 1 made of anodizedaluminum and shaped in semi-circu lar form. This connecting strip isintended for use as a structural element for a bank of contacts of arotary selector for use in automatic telephone systems. The strip lcomprises a number of equally spaced bores 2 which are parallel with theplane of the strip and all I are directed to the center of' curvaturethereof; Contact members constituted by lengths of metal wire 3 whichproject beyond the end of the supporting strip 1 on either side arearranged" in these bores.' The lengths of wire are centered in the bores2 by means of a hard insulating mass 5, in this case polystyrene. Thelengths of wire are anchored in the polystyrene in that the partsenclosed in the bores locally comprise a flat part l2. The insulatingmass S in each bore is anchored with respect to the support l in thatthis mass ills not only the bore itself but also the transverseapertures 4 which act as charging holes for the insulating mass inmanufacture. The polystyrene 5 which centers a length of 'wire 3` in abore at the ends of the bore hasta bulge 6 which surrounds the length ofwire conically and increases the creeping path between the supportingstrip l and the length of wire.

Fig. 4 is a cross-sectional view or" a second embodiment of theconnecting strip according to the invention. The difference from theembodiment shown in Figs; l, 2 and 3 is that no charging holes 4 areprovided but the support l comprises a channel-shaped recess 13` whichruns substantially throughout the length of the support and into whichall bores 2 open. The insulating mass 5 also iills this recess and thusgoes on at one side of the support.

Not all the contact members 3 arranged in the supporting strip l areshown in Fig. 1. Those shown are divided in three groups A, B and Cwhich show the contact members 3 in different stages of manufacturing.As has been stated hereinbefore, in the embodiment shown all contactmembers arranged in the supporting strip in actual fact are shaped inthe form indicated with respect to those of the group C.

The contact members 3 of group A consist of straight lengths of metalwire of identical cross-section throughout their length.

The contact members of group B consist of lengths of wire such as thosein group A, both ends of the lengths, however, being ilattened. Thusflat end parts 7 and 8 are obtained which lie in one plane. The parts 7and 8 may be formed previously to the insertion of the lenghs of wire inthe supporting strip, however, it is simpler to insert lengths of wirelike those of group A into the supporting strip first and then toflatten the ends of these lengths all together in one operation.

The contact members in the group C are shaped into their final form bypunching the attened endsV of the lengths of wire secured in thesupporting strip 1 (group B) to the correct size by means of aspeciiically made cutting tool. The correct relative arrangement of thecutting tool and the connecting strip is obtained with theA aid oflocating holes formed in the ends of the supporting strip l. In thispunching operation the ends of the wire segments which are situated atthe inner side of the strip are shaped into the form of substantiallyrectangular ilat contact planes l0 which are very accurately spaced andare intended to be swept by a brush in a selector, the bank of contactsof which is built up from such connecting strips. As may be seen at 9this punching process causes the flattened ends 7 of the lengths of wireto be shaped so as to exhibit a profile which facilitates the attachmentof connecting wires to these ends, for example by soldering.

In view of a satisfactory contact between the contacts 10 and thefbrushsliding thereon in a selector built up from a number of the describedconnecting strips it may be. desirable for the contact surfaces toconsist of precious metal, for example palladium or silver. This `may beobtained by making that end of the length of some other manner a lengthof previous metal wire to 'g5 the lengths of wire consisting of basemetal, for example brass; which are to be arranged in the bores 2 or bypreviously providing the ends concerned of these lengths of wire with asheath of precious metal.

In the embodiment described the supporting strip l is semicircular sothat the connecting strip may act as a structural element of asemi-cylindrical bank of contacts. However, the supporting strip may beshaped in a ditferentfo'rm, for example in a straight form so as toenable the strip to act as a structural element for a straight bank ofcontacts.

The connecting strip according to the invention may also' be used ina'diierentmanner than as a structural element for a Ibank. ofV contacts.It may, for example, be used as a distributing strip in telephoneexchanges, as a mounting support for electric parts in an apparatus andas a connectingv strip for the energizing windings of anelectro-magnetic relay. In relays the contact springs are usuallygripped between insulating spacers which are mounted on a connectingstrip which is secured to the yoke and comprises Contact members for theenergizing coils. Due to tolerances in thickness in the connecting stripthe contact springs do not always occupy the correct position withrespect to the parts moving them which are coupled to the armaturethereby necessitating adjustment of the contact springs. By the use ofthe connecting strip according to the invention which can bemanufactured and reproduced with great accuracy of the aforesaidthickness this disadvantage is overcome.

While I have shown and described the preferred embodiment of myinvention, it will be understood that the latter may be embodiedotherwise than as herein specilically illustrated or described and thatin the illustrated embodiment certain changes in the details ofconstruction and in theV arrangement of parts may be made Withoutdeparting from the underlying idea or principle of the invention Withinthe scope of the appended claims.

What is claimed is:

l. A connecting strip for a bank of contact members insulated from oneanother comprising said connecting strip being integral and composed ofmetal and having a plurality of bores therein transverse to thelongitudinal axis of said connecting strip and parallel with the planeof said strip, an insulating mass for permanently and preciselycentering each of said contact members in said bore in such a mannerthat the ends of each of said contact members project beyond theadjacent side of said connecting strip.

2. A connecting strip as set forth in claim l wherein said strip iscomposedofaluminum.

3. A connecting strip forV a bank of Contact members insulated from oneanother comprising said connecting strip being integral and composed ofmetal and having a plurality of bores therein transverse to thelongitudinal axis of said connecting strip and parallel with the planeof said strip, an insulating mass yfor permanently and preciselycenteringeach of said contact members in said bore in such a manner thatthe ends of each of said contact members project beyond the adjacentside of said connecting strip, said contact members being lengths ofWire and said insulating mass at the end of each of saidbores beingprovided with a conical bulge surrounding the length of wire centered ineach bore.

4. A connecting strip for a bank of contact members insulated from oneanother comprising said connecting strip being integral and composed ofmetal and having a plurality of bores therein transverse to thelongitudinal axis' of said connecting strip' and parallel with the planeof said strip, an insulating mass for permanently andprecisely'centering each of said contact members in said bore in such amanner that the endsfof each of said contact members project beyond theadjacent side of said connecting strip, said contactmembers beinglengths of wire which are imbeddedfin the insulating mass, each of 5said lengths of wire having one flattened end for attaching connectingwires thereto.

5. A connecting strip for a bank of contact members insulated from oneanother comprising said connecting strip being integral and composed ofmetal and having a plurality of bores therein transverse to thelongitudinal axis of said connecting strip and parallel to the plane ofSaid strip, an insulating mass for permanently and precisely centeringeach of said contact members in said bore in such a manner that the endsof each of said contact members project beyond the adjacent side of saidconnecting strip, said contact members being lengths of Wire which areimbedded in the insulating mass, each of said wires having at one end acoating of precious metal, the other part of said Wire being a basemetal.

6. A connecting strip for a bank of contact members insulated from oneanother comprising said connecting strip being integral and composed ofmetal and having a plurality of bores therein transverse to thelongitudinal axis of said connecting strip and parallel to the plane ofsaid strip, an insulating mass for permanently and precisely centeringeach of said contact members in said bore in such a manner that the endsof each of said contact members project beyond the adjacent side of saidconnecting strip, said contact members being lengths of wire imbedded insaid insulating mass, and at one side of said connecting strip the endsof each of the lengths of Wire are flattened.

References Cited in the le of this patent UNITED STATES PATENTS1,178,207 Baldwin Apr. 4, 1916 1,557,615 RichterA Oct. 20, 19251,595,107 Lyng Aug. 10, 1926 2,294,482 Siegmund Sept. 1, 1942 2,534,864Fritts Dec. 19, 1950 FOREIGN PATENTS 197,486 Great Britain May 17, 1923433,597 Germany May 2, 1924

